Diffuse reflection is a term used in physics to describe how an incident ray is reflected at many different angles rather than at just one angle, as in the case of specular reflection.  The Profusion flash diffuser makes use of diffuse reflection in its novel dimpled bounce surfaces.  The rear, left, and right bounce panels all have a dimpled surface that greatly increases diffuse reflection.  The result is a noticeably softer light, while retaining its intensity.  Compare this to bulky "shoot through" diffusers that absorb large amounts of energy and light, forcing the photographer to compensate in burdensome ways.